A primary purpose of the no-huddle offense is to allow quarterback Tom Brady, a 13-year veteran, extra time to survey an on-its-heels defense and adjust accordingly.

Photo: Bill Kostroun, Associated Press

A primary purpose of the no-huddle offense is to allow quarterback...

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Tom Brady typically chooses from six one-word play calls when running the no-huddle offense. The Serra High grad is in his 13th season in the NFL.

Photo: Robert Duyos, McClatchy-Tribune News Service

Tom Brady typically chooses from six one-word play calls when...

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MIAMI GARDENS, FL - DECEMBER 02: Tom Brady #12 of the New England Patriots calls a play during a game against the Miami Dolphins at Sun Life Stadium on December 2, 2012 in Miami Gardens, Florida. (Photo by Mike Ehrmann/Getty Images)

Photo: Mike Ehrmann, Getty Images

MIAMI GARDENS, FL - DECEMBER 02: Tom Brady #12 of the New England...

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New England Patriots quarterback Tom Brady (12) calls out the defense during the first half of an NFL football game against the New York Jets Thursday, Nov. 22, 2012 in East Rutherford, N.J. (AP Photo/Bill Kostroun)

Photo: Bill Kostroun, Associated Press

New England Patriots quarterback Tom Brady (12) calls out the...

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{2012-12-02_nfl_49ers_vs_rams_0420} December 2, 2012: Patrick Willis (52) of the 49ers during the NFL game between the San Francisco 49ers vs the St. Louis Rams at the Edward Jones Dome in St. Louis Missouri. By Danny Reise/SPECIAL TO THE CHRONICLE

Photo: Danny Reise, SFC

{2012-12-02_nfl_49ers_vs_rams_0420} December 2, 2012: Patrick...

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Brady and receiver Brandon Lloyd savor a moment in the Patriots' 42-14 humbling of Houston on Monday night.

In a 31-21 win at Denver in October, the Patriots ran a whopping 89 plays, collected a franchise-record 35 first downs and rarely said "Ready, break": On their five scoring drives, they operated without a huddle on 41 of 59 plays.

Two months later, the effects of their breakneck attack were again on display in the fourth quarter of Monday's 42-14 win over the Texans. ESPN cameras captured Houston defensive end J.J. Watt gasping for breath because New England didn't stop for air.

Next to face the no-huddle will be the 49ers, who will arrive in Foxborough, Mass., on Sunday night with one of the NFL's best defenses. Their challenge, at times, will be to keep up with the league's top-ranked offense, a unit that's wildly successful when it speeds up the pace.

"It's very good," 49ers head coach Jim Harbaugh said. "They've got a good system for it and they do a real good job with it. I can't think of another team that's better at it."

The maestro of New England's no-huddle, of course, is quarterback Tom Brady.

According to a Boston Globe story this season, Brady typically chooses from six one-word play calls when running the no-huddle. That word tells the rest of the offense details ranging from formation to snap count to blocking schemes.

The benefits? For starters, it makes it difficult for an opponent to make substitutions, although 49ers defensive coordinator Vic Fangio said that's not the Patriots' main motivation. And though defenses can get gassed trying to keep pace, that's merely a fringe benefit.

A primary purpose is to allow Brady, a 13-year veteran who will be playing in his 175th career regular-season game, extra time to survey an on-its-heels defense and adjust accordingly.

"It makes a defense kind of declare what they're going to do," Patriots wide receiver Wes Welker said. "It helps us get set up and it's tough for them to disguise things."

Fangio said the Patriots will vary the tempo. On one play, Brady will assess the landscape as the play clock ticks down. On the next play, he'll take the snap as the defense is getting set.

"It gives Brady a longer look at how you're aligning to their formations," Fangio said. "And then they'll try and speed it up. Try and get you confused to where a play will be over and, bam, they'll try and get the next play run immediately. So, it's just to keep you on edge."

In practice this week, the 49ers are maintaining the status quo. Third-string quarterback Scott Tolzien, who runs the scout-team offense, said there hasn't been added emphasis on defending the no-huddle.

"It's been no more than a usual week," Tolzien said. "Any team can do it, so Vic just sprinkles it in here and there."

Perhaps part of the reasoning is that's it hard to simulate Brady orchestrating a hurry-up offense at the line of scrimmage. The 49ers will get the real thing Sunday night and inside linebacker NaVorro Bowman pledges to be prepared.

"You have to really be on it, be able to think fast out there" Bowman said. "And having a good quarterback like Tom Brady, it makes it more difficult. We've been gearing up for it. We know they like to do it, and I think we'll handle it well."